Reusable baby bottles or hard bottles, such as made of glass or plastic, have been commonly used to feed babies formula, water, and other liquids. After liquid is placed in the bottle, a nipple is attached to the bottle and the assembly is ready for use. A hard bottle sometimes is cleaned and sterilized between each use, requiring substantial time and effort.
An alternative to a hard bottle is the disposable liner or sac (also referred to as a "disposable bottle") that is used in conjunction with a holder which supports the liner. The liner, which is used only once, is pre-sterilized, and is inserted into the holder. The liner is then filled with liquid, and a nipple is attached to the holder. This alternative is economical and sanitary, and greatly minimizes the time and effort required to prepare for feeding a baby.
One limitation inherent in hard bottles is the tendency of babies to ingest substantial amounts of air when ingesting the liquid. This air can cause uncomfortable distention and gas in the baby's stomach, and may lead to vomiting and other problems. Disposable liners collapse as liquid is drawn out, thus minimizing the amount of air the baby ingests. However, under some circumstances a small amount of air can be drawn in to the liner through the hole of the nipple.
Attempts have been made to address this problem. U.S. Pat. No. 3,998,348 to Sammaritano provides a roller assembly attached to the lower, closed end of the liner to take up the liner as it empties. U.S. Pat. No. 4,796,767 provides a pushrod stored on the outside of the holder. When in use, the pushrod is inserted through the open bottom of the holder to press air out of the liner through the attached nipple feeding hole. U.S. Pat. No. 4,176,754 to Miller provides a donut-shaped pneumatic roller used to press air out of the liner as discussed above.
Some patents provide a plunger-type insert having the general shape of the inside of the holder. The plunger can be pushed up within the holder to press air out of the liner. Certain devices use a plunger having a stem extending from the open bottom of the holder. Other devices require the user to reach inside the open bottom of the holder to operate the plunger.
Other patents provide a refinement on this construction employing a plunger-type insert that is operable by means located on the sides of the holder. U.S. Pat. No. 5,356,016 to Wiedemann provides a flat, circular plunger member having a pair of tab handles on its diameter that extend through a pair of longitudinal slots in the holder.
U.S. Pat. No. 3,955,698 to Hammer is a device somewhat similar to that shown in the Wiedemann patent. However, the Hammer device has a pair of tab handles that engage with ratcheted indentations on the interior surface of the holder. U.S. Pat. No. 5,301,825 to Di Scala et al. provides a related device in which the tab handles are connected in a ring extending around the holder.
The early devices appear to be unwieldy, unstable or awkward. The three latter devices have several limitations. First, each requires a complex disassembly of the tab or ring handles to clean the holder assembly. This is inconvenient and time-consuming for the user. Also, the devices with small tab handles are removable, and can pose a danger to the baby as small parts. Second, each device requires two hands to operate properly. The tab handle devices require the user to hold the holder in one hand, and apply pressure, preferably with the other hand, to the opposing tab handles simultaneously. The ring device requires the user to grasp the holder in one hand, and the ring, preferably with the other hand and at opposing points, to slide it. If used with one hand, slight movements of the ring might be possible, but any greater pressure may force the ring's edge into the holder surface and arrest further movement. Third, each device is bulkier than the present holder thereby making these known devices less attractive and, presumably, more expensive to make.